Semiconductor apparatus with multiple tiers, and methods

ABSTRACT

Apparatus and methods are disclosed, including an apparatus that includes a number of tiers of a first semiconductor material, each tier including at least one access line of at least one memory cell and at least one source, channel and/or drain of at least one peripheral transistor, such as one used in an access line decoder circuit or a data line multiplexing circuit. The apparatus can also include a number of pillars of a second semiconductor material extending through the tiers of the first semiconductor material, each pillar including either a source, channel and/or drain of at least one of the memory cells, or a gate of at least one of the peripheral transistors. Methods of forming such apparatus are also described, along with other embodiments.

PRIORITY APPLICATION

This application is a continuation of U.S. application Ser. No.16/806,755, filed Mar. 2, 2020, which is a divisional of U.S.application Ser. No. 15/645,635, filed Jul. 10, 2017, now issued as U.S.Pat. No. 10,580,790, which is a divisional of U.S. application Ser. No.14/511,340, filed Oct. 10, 2014, now issued as U.S. Pat. No. 9,704,876,which is a divisional of U.S. application Ser. No. 13/096,822, filedApr. 28, 2011, now issued as U.S. Pat. No. 8,860,117, all of which areincorporated herein by reference in their entirety.

BACKGROUND

Semiconductor constructions with multiple tiers are used in manyelectronic devices such as personal digital assistants (PDAs), laptopcomputers, mobile phones and digital cameras. Some of thesesemiconductor constructions have arrays of charge storage transistors.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments are illustrated by way of example and not limitation inthe figures of the accompanying drawings in which:

FIG. 1 is a three-dimensional view of a semiconductor memory deviceaccording to various embodiments of the invention;

FIG. 2 is a front view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 3 is a front view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 4 is a front view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 5 is a top view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 6 is a top view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 7 is a top view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 8 is a top view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 9 is a top view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 10 is a top view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 11 is a three-dimensional view of decoder transistors according tovarious embodiments of the invention;

FIG. 12 is a three-dimensional view of memory cells according to variousembodiments of the invention;

FIG. 13 is a schematic view of a semiconductor construction according tovarious embodiments of the invention;

FIG. 14 is a top view of a semiconductor construction according tovarious embodiments of the invention.

FIG. 15 is a cross-sectional view of a semiconductor constructionaccording to various embodiments of the invention.

FIG. 16 is a cross-sectional view of a semiconductor constructionaccording to various embodiments of the invention.

FIG. 17 is a perspective view of a semiconductor memory device accordingto various embodiments of the invention.

FIG. 18 is a schematic view of a semiconductor construction according tovarious embodiments of the invention.

FIG. 19 is a cross-sectional view of a semiconductor constructionaccording to various embodiments of the invention.

FIG. 20 is a cross-sectional view of a semiconductor constructionaccording to various embodiments of the invention.

FIG. 21 is a cross-sectional view of a semiconductor memory deviceaccording to various embodiments of the invention.

FIG. 22 is a cross-sectional view of a semiconductor memory deviceaccording to various embodiments of the invention.

FIG. 23 is a flow diagram of methods according to various embodiments ofthe invention; and

FIG. 24 is a diagram illustrating a system according to variousembodiments of the invention.

DETAILED DESCRIPTION

The density of components in three-dimensional semiconductor devicescontinually increases with the competition for increasing sales of thedevices. The inventor has discovered that the challenge noted above, aswell as others, can be addressed by fabricating, in each tier of aplurality of tiers of semiconductor material, at least a respectiveportion of a respective first device and at least a portion of arespective second device. For example, a portion of a three-dimensionaltransistor for a peripheral circuit, such as an access line decodercircuit or a data line multiplexing circuit, and a portion of athree-dimensional memory cell are fabricated in the same tier ofsemiconductor material of a memory device. The resulting memory devicecan provide an increased density of memory cells without significantadditional processing events to fabricate the transistors of at leastone peripheral circuit.

FIG. 1 is a three-dimensional view of a semiconductor memory device 100according to various embodiments of the invention. The memory device 100can be formed on a substrate 106 and includes multiple tiers ofsemiconductor material that include access lines 110, 112, 114 and 116that at least partially surround charge storage structures (e.g.,floating gates) of charge storage transistors. For the purposes of thisdocument, a “tier of semiconductor material” can mean semiconductormaterial formed in a same plane, rank, row, or unit, such as in ahorizontal or vertical or sloped plane, row, rank or unit of astructure. Two U-shaped pillars 118 and 120 are formed in the device 100and can function as channels for the charge storage transistors. TheU-shaped pillars 118 and 120 can extend into the substrate 106. Verticalslots 124 separate charge storage transistors and their access lines110, 112, 114 and 116 that at least partially surround each U-shapedpillar 118 and 120. Each U-shaped pillar 118 and 120 comprises asemiconductor material such as silicon or polysilicon (e.g., a tube ofsilicon or polysilicon with a core, where the core may be filled withair or a dielectric material). A single tier of select gates 130surround select transistors formed at both ends of each of the U-shapedpillars 118 and 120. Source lines 138 are formed on the selecttransistors at first ends of the U-shaped pillars 118 and 120. Datalines 144 are formed on the select transistors at second ends of theU-shaped pillars 118 and 120. The tiers of semiconductor materialincluding the access lines 110, 112, 114 and 116 may also each functionas a body of a peripheral transistor, such as a decoder transistor. TheU-shaped pillars 118 and 120 may comprise a semiconductor material thatalso functions as gate of a peripheral transistor as shown and describedwith reference to the following FIGS. 2-16 .

FIG. 2 is a front view of the semiconductor construction 200 accordingto various embodiments of the invention. The same tiers and regions inthe semiconductor construction 200 will be identified by the samereference numerals throughout FIGS. 2-10 for purposes of brevity andclarity. The semiconductor construction 200 can be formed on asemiconductor (e.g., silicon) substrate 206. Tiers of a semiconductormaterial such as n-type polysilicon are deposited alternately with adielectric (not shown) on the substrate 206. The tiers of semiconductormaterial include first 210, second 214, third 218, fourth 222 and fifth226 tiers. The dielectric may be, for example, silicon dioxide that isused to separate the tiers of semiconductor material 210, 214, 218, 222and 226 from each other and the substrate 206. The tiers ofsemiconductor material 210, 214, 218, 222 and 226 (referred tohereinafter by example as tiers of polysilicon) are in a stackedarrangement. The semiconductor construction 200 may include, forexample, even numbers, such as 8, 16, 24, 32, 40, 48 or more, of tiersof polysilicon formed alternately with the dielectric. Although theembodiments discussed herein involve tiers of n-type polysilicon, thetiers of polysilicon may alternatively be undoped or p-type polysiliconaccording to various embodiments of the invention.

FIG. 3 is a front view of the semiconductor construction 200 accordingto various embodiments of the invention. A vertical slot 302 is etchedthrough the tiers 210, 214, 218, 222 and 226 to divide the semiconductorconstruction 200 into, for example, a left-hand construction 304 and aright-hand construction 308. The left-hand construction 304 and theright-hand construction 308 may be different in size and/or theconstruction 200 may be further divided into additional constructions.For example, the left-hand construction 304 may comprise about seventyto eighty percent of the semiconductor construction 200 while theright-hand construction 308 may comprise about five percent of thesemiconductor construction 200. The vertical slot 302 is large enoughfor interconnect lines (e.g., wires) to be formed between the left-handconstruction 304 and the right-hand construction 308. The left-handconstruction 304 includes first portions 310, 314, 318, 322 and 326 ofthe tiers 210, 214, 218, 222, and 226, respectively, while theright-hand construction includes second portions 340, 344, 348, 352 and356 of the tiers 210, 214, 218, 222, and 226, respectively.

FIG. 4 is a front view of the semiconductor construction 200 accordingto various embodiments of the invention. The left-hand construction 304and the right-hand construction 308 are each formed (e.g., etched) intoa staircase configuration. As a result, the first portion 310 is longerthan the first portion 314, the first portion 314 is longer than thefirst portion 318, the first portion 318 is longer than the firstportion 322 and the first portion 322 is longer than the first portion326 of the tiers 210, 214, 218, 222, and 226, respectively, in theleft-hand construction 304. The second portion 340 is longer than thesecond portion 344, the second portion 344 is longer than the secondportion 348, the second portion 348 is longer than the second portion352 and the second portion 352 is longer than the second portion 356 ofthe tiers 210, 214, 218, 222, and 226, respectively, in the right-handconstruction 308.

FIG. 5 is a top view of the semiconductor construction 200 describedwith respect to FIG. 4 .

FIG. 6 is a top view of the semiconductor construction 200 according tovarious embodiments of the invention. The left-hand construction 304 andthe right-hand construction 308 are formed into an array of memory cellsand peripheral transistors, respectively, such as by different etchactivities. A vertical slot 637 can be etched through the right-handconstruction 308 to leave, for example, a first decoder block 654 and asecond decoder block 658. The left-hand construction 304 can be etchedinto a first set of fingers 672 and a second set of fingers 678 that areinterdigitally arranged. The first set of fingers 672 and the second setof fingers 678 are separated from each other such that each of the firstportions 310, 314, 318, 322 and 326 of the tiers 210, 214, 218, 222, and226, respectively, are separated into two parts. Each separate part ofeach first portion 310, 314, 318 and 322 can function as an access linefor a memory cell. Less than all of the first portions 310, 314, 318,322 and 326 of the tiers 210, 214, 218, 222, and 226, respectively, areshown in FIG. 6 for purposes of brevity and clarity.

Polysilicon from the first portions 314, 318 and 322 of the tiers 214,218 and 222, respectively, is shown in the first set of fingers 672.Polysilicon from the first portions 310, 314 and 318 of the tiers 210,214, and 218, respectively, is shown in the second set of fingers 678.The polysilicon from the first portion 326 of the tier 226 is formed(e.g., etched) into elongated and substantially parallel select gates680, 682, 684, 686, 688, 690, 692, 694, 696 and 698. Two of the selectgates 680, 682, 684, 686, 688, 690, 692, 694, 696 and 698 are in each ofthe fingers of the first set of fingers 672 and the second set offingers 678.

FIG. 7 is a top view of the semiconductor construction 200 according tovarious embodiments of the invention. Holes 782 are etched through thefirst portions 310, 314, 318, 322 and 326 of the tiers 210, 214, 218,222, and 226, respectively, in the second set of fingers 678. Similarholes 788 are etched through the first portions 310, 314, 318, 322 and326 of the tiers 210, 214, 218, 222, and 226, respectively, in the firstset of fingers 672. The holes 782 and 788 are etched to accommodateU-shaped pillars of a semiconductor material in the left-handconstruction 304, and are approximately the same size in someembodiments of the invention.

Each of the second portions 340, 344, 348, 352 and 356 of the tiers 210,214, 218, 222, and 226, respectively, in the first decoder block 654 andthe second decoder block 658 of the right-hand construction 308functions as a body (a source, a channel and/or a drain) of a decodertransistor that is to be coupled to an access line of a memory cell or aselect gate. Multiple holes 794 are etched through all of the secondportions 340, 344, 348, 352 and 356 of the tiers 210, 214, 218, 222, and226, respectively, in each of the first decoder block 654 and the seconddecoder block 658 to accommodate pillars (e.g., of polysilicon material)that can function as gates of multi-gate decoder transistors. The holes794 may be formed separately and/or larger than the holes 782 and/or 788in the left-hand construction 304, such as to provide for higher drivingcurrent in the decoder transistors. Some or all of the decodertransistors of the right-hand construction 308 may also be single-gatedecoder transistors. The holes 794 in the right-hand construction 308may also be substantially the same size and/or may be formed atsubstantially the same time as the holes 782 or 788 in the left-handconstruction 304 according to various embodiments of the invention.

FIG. 8 is a top view of the semiconductor construction 200 according tovarious embodiments of the invention. Memory cell transistors in theleft-hand construction 304 include charge storage structures (e.g.,charge traps or floating gates) that are formed in the holes 782 and788. The memory cell transistors may be formed by depositing aninter-poly dielectric, a storage element such as floating gate andsilicon nitride (SiN), a tunnel oxide and a polysilicon layer in theleft-hand construction 304 while the right-hand construction 308 iscovered to shield it from the depositions. U-shaped pillars 810 of asemiconductor material are formed in the holes 782 and 788 in theleft-hand construction 304 for the memory cells. Each U-shaped pillar810 extends from the first set of fingers 672 to the second set offingers 678 and functions as a body (a source, a channel and/or a drain)of several memory cell transistors in the fingers 672 and 678; forexample, where there is one memory cell transistor for each access line.Each U-shaped pillar 810 comprises, for example, silicon or polysilicon(e.g., a tube of silicon or polysilicon with a core, where the core maybe filled with air or a dielectric material). The charge storagestructures (e.g., charge traps or floating gates) are formed in theholes 782 and 788 around the U-shaped pillars 810.

Gates (e.g., comprising polysilicon) (not shown) for decoder transistorsare formed in the holes 794 in the second portions 340, 344, 348, 352and 356 of the tiers 210, 214, 218, 222, and 226 of the first decoderblock 654. Likewise, gates for decoder transistors are formed in theholes 794 in the second portions 340, 344, 348, 352 and 356 of the tiers210, 214, 218, 222, and 226 of the second decoder block 658. The gatesmay be formed by depositing a dielectric material such as silicondioxide followed by a polysilicon layer to form a gate oxide and thegates, respectively, while the left-hand construction 304 is covered toshield it from the depositions. The gates may be deposited and etched asseparate gates, or may be deposited and etched as a single gate for boththe first decoder block 654 and the second decoder block 658.

Polysilicon may be deposited for the U-shaped pillars 810 in theleft-hand construction 304 and the gates for the decoder transistors inthe first decoder block 654 and/or the second decoder block 658 at thesame time or in separate steps.

Lines 882 are formed to couple to the gates (not shown) for decodertransistors in the first decoder block 654 and the second decoder block658. The polysilicon of the U-shaped pillars 810 in the left-handconstruction 304 may also be the gates for the decoder transistors inthe first decoder block 654 or the second decoder block 658. The lines882 may be, for example, tungsten, aluminum or copper. The lines 882 maybe replaced by semiconductor lines such as polysilicon lines.

Data lines 826 and source lines (not shown), such as those comprisingmetal or doped polysilicon, are formed in respective contact with theopposing ends of the U-shaped pillars 810 in the holes 782 and 788 inthe left-hand construction 304. The data lines 826 may be arranged to besubstantially parallel to each other and substantially perpendicular tothe select gates 680, 682, 684, 686, 688, 690, 692, 694, 696 and 698.The data lines 826 comprise metal or polysilicon. The first portions310, 314, 318 and 322 of the tiers 210, 214, 218 and 222, respectively,each function as an access line to a respective memory celltransistor(s) formed in and around each of the U-shaped pillars 810. Themetal may be, for example, titanium nitride (TiN), tantalum (Ta),tantalum nitride (TaN) or Tungsten (W).

For purposes of brevity and clarity, the coupling of the decodertransistors of the first decoder block 654 to access lines and selectlines is not shown in FIG. 8 . The decoder transistors of the seconddecoder block 658, however, are shown coupled to access lines of thefirst portions 310 and 314 of the tiers 210 and 214, respectively, andthe select gates 684 and 686 by lines 840, 850, 860 and 870. The lines840, 850, 860 and 870 may be formed at the same time and/or from thesame material used to form data lines 826 or source lines (not shown),such as, for example, polysilicon, tungsten, aluminum or copper. Inanother embodiment, data lines 826 or source lines (not shown) and lines840, 850, 860 and 870 may be formed at different times and/or fromdifferent materials. As depicted, line 840 is formed to couple the firstportion 310 to the second portion 340. The line 850 is formed to couplethe first portion 314 to the second portion 344. The line 860 is formedto couple the select gate 684 to the second portion 348. The line 870 isformed to couple the select gate 686 to the second portion 352. Forbrevity and clarity, the coupling of other access lines and select gatesof the left-hand construction 304 to decoder transistors is not shown.The semiconductor construction 200 shown in FIGS. 2-8 is arranged suchthat the access lines of the first portions 310, 314, 318 and 322 of thetiers 210, 214, 218 and 222, respectively, are stacked with respect toeach other.

FIG. 9 is a top view of the semiconductor construction 200 according tovarious embodiments of the invention. The left-hand construction 304 isthe same as the left-hand construction 304 shown in FIG. 7 , and theright-hand construction 308 is the same as the right-hand construction308 shown in FIG. 6 before holes are etched as described above. The samereference numerals identify the same elements for purposes of brevityand clarity.

Each of the second portions 340, 344, 348, 352 and 356 of the tiers 210,214, 218, 222, and 226, respectively, in the first decoder block 654 andthe second decoder block 658 of the right-hand construction 308functions as a body (a source, a channel and/or a drain) of a decodertransistor that is to be coupled to an access line of a memory cell.Holes 910 are etched through all of the second portions 340, 344, 348,352 and 356 of the tiers 210, 214, 218, 222, and 226, respectively, inthe first decoder block 654 and the second decoder block 658 toaccommodate polysilicon gates of the decoder transistors. The holes 910in the right-hand construction 308 are the same size as the holes 782 or788 in the left-hand construction 304 and are etched at the same time.Multiple rows and columns of the holes 910 are etched to enable a higherdriving current through the right-hand construction 308.

Gates may be formed by depositing a dielectric material such as silicondioxide followed by a polysilicon layer in the right-hand construction308 to form a gate oxide and the gates while the left-hand construction304 is covered to shield it from these depositions. The gates may bedeposited and etched as separate gates, or may be deposited and etchedas a single gate for both the first decoder block 654 and the seconddecoder block 658. Memory cell transistors may be formed by depositingan inter-poly dielectric, a storage element such as a floating gate andSiN, a tunnel oxide and a polysilicon layer in the left-handconstruction 304 while the right-hand construction 308 is covered toshield it from these depositions.

FIG. 10 is a top view of the semiconductor construction 200 according tovarious embodiments of the invention. U-shaped pillars 1010 of asemiconductor material are formed in the holes 782 and 788 in theleft-hand construction 304 for the memory cells as shown in FIG. 7 .Data lines 1026 and source lines (not shown), such as those comprisingmetal or doped polysilicon, are formed in respective contact with theopposing ends of the U-shaped pillars 1010 in the holes 782 and 788 inthe left-hand construction 304 as shown in FIG. 10 . The data lines 1026may be arranged to be substantially parallel to each other andsubstantially perpendicular to the select gates 680, 682, 684, 686, 688,690, 692, 694, 696 and 698. The first portions 310, 314, 318 and 322 ofthe tiers 210, 214, 218 and 222, respectively, each function as anaccess line to a respective memory cell transistor(s) formed in andaround each of the U-shaped pillars 1010.

Lines 1082 are formed through the holes 910 of the first decoder block654 and the second decoder block 658 to couple to the gates of thedecoder transistors. The polysilicon of the U-shaped pillars 1010 in theleft-hand construction 304 may also be the gates for the decodertransistors in the first decoder block 654 or the second decoder block658. The lines 1082 may be, for example, tungsten, aluminum or copper.The lines 1082 may be replaced by semiconductor lines such aspolysilicon lines.

The decoder transistors of the first decoder block 654 are to be coupledto memory cell transistors not shown in FIG. 10 . The decodertransistors of the second decoder block 658 are coupled to access linesof the first portion 310 and the first portion 314 and the select gates684 and 686 by lines 1040, 1050, 1060 and 1070. The lines 1040, 1050,1060 and 1070 may be, for example, tungsten, aluminum or copper. Thelines 1040, 1050, 1060 and 1070 may be replaced by a semiconductor suchas polysilicon. The line 1040 is routed to couple the first portion 310to the second portion 340. The line 1050 is routed to couple the firstportion 314 to the second portion 344. The line 1060 is routed to couplethe select gate 684 to the second portion 348. The line 1070 is routedto couple the select gate 686 to the second portion 352. The otheraccess lines and select gates of the left-hand construction 304 arecoupled to decoder transistors not shown. The semiconductor construction200 shown in FIGS. 2-10 is arranged such that the access lines of thefirst portions 310, 314, 318 and 322 of the tiers 210, 214, 218 and 222,respectively, are stacked with respect to each other.

The polysilicon used to form the access lines in the first portions 310,314, 318 and 322 of the tiers 210, 214, 218, 222, and 226, respectively,may have the same or a different implant concentration than thepolysilicon of the bodies of decoder transistors in the second portions340, 344, 348, 352 and 356 of the tiers 210, 214, 218, 222, and 226,respectively. Also, although the previous description focused onembodiments where both access lines and bodies of the decodertransistors are formed from polysilicon, in other embodiments, theaccess lines may be replaced by metal. In such cases, at least a portionof one of constructions 304 or 308 may be masked while the otherconstruction or portion of the construction 304 or 308 is processed.

The semiconductor construction 200 comprises access lines of memorycells and bodies of peripheral transistors, such as decoder transistorsin the same tiers of semiconductor material. Gates of the decodertransistors may also be formed from the same semiconductor materialdeposited to form bodies of the memory cells.

The embodiments of the semiconductor construction 200 shown in FIGS. 2to 10 are examples of the semiconductor memory device 100 shown in FIG.1 according to various embodiments of the invention.

FIG. 11 is a three-dimensional view of decoder transistors 1100according to various embodiments of the invention that are examples ofthe decoder transistors in the decoder blocks 654 and 658 shown in FIGS.6-10 . Three decoder transistors 1102, 1104 and 1106 are formed in threetiers 1110, 1120 and 1130 of polysilicon. The tiers 1110, 1120 and 1130are arranged one above the other in a staircase configuration. The tier1130 is larger than the tier 1120 above it, and the tier 1120 is largerthan the tier 1110 above it. The tiers 1110, 1120 and 1130 are separatedfrom each other by a dielectric such as silicon dioxide (not shown).Polysilicon, for example, can be used to form a block select line 1150above the tiers 1110, 1120 and 1130, and two gates 1160 are formed inholes (e.g., holes 794) in the tiers 1110, 1120 and 1130. Portions ofthe tiers 1110, 120 and 1130 on one side of the line 1150 function asdrains 1170 for the decoder transistors 1102, 1104 and 1106. Portions ofthe tiers 1110, 1120 and 1130 on a second side of the line 1150 functionas sources 1180 for the decoder transistors 1102, 1104 and 1106.Polysilicon in the tiers 1110, 1120 and 1130 between the sources 1180and the drains 1170 function as channels for the decoder transistors1102, 1104 and 1106.

FIG. 12 is a three-dimensional view of memory cells according to variousembodiments of the invention that are examples of memory cells andportions of the U-shaped pillars 810 in the left-hand construction 304shown in FIGS. 8 and 10 . FIG. 12 shows six three-dimensional memorycells 1206. Each memory cell 1206 is a charge storage transistorincluding a ring of p+ type polysilicon 1210 that functions as afloating gate. The rings of p+ type polysilicon 1210 are separated fromeach other by tiers of dielectrics 1220. Polysilicon pillars 1230 passthrough the rings of p+ type polysilicon 1210, and are separated fromtheir respective rings by tunnel dielectric 1228. Between the tiers ofdielectric material 1220, each of the rings of p+ type polysilicon 1210are surrounded by an inter-poly dielectric (IPD) 1236, such as onecomprising silicon dioxide, silicon nitride (Si₃N₄) and silicon dioxide(ONO), and a respective polysilicon access line 1240. The tiers ofdielectrics 1220 and the tunnel dielectric 1228 may be, for example,silicon dioxide. The memory cells 1206 are arranged such that the accesslines 1240 are stacked. The access lines 1240 may comprise metal and notpolysilicon.

FIG. 13 is a schematic view of a semiconductor construction 1300according to various embodiments of the invention. The semiconductorconstruction 1300 includes an array 1302 of memory cells and fourdecoder blocks of decoder transistors, a first decoder block 1312, asecond decoder block 1314, a third decoder block 1316 and a fourthdecoder block 1318. The array 1302 is divided into a first array 1304and a second array 1306 of memory cells each having fingers that areinterdigitally arranged. Each of the array 1302 and decoder blocks 1312,1314, 1316 and 1318 are formed in nine tiers 1330, 1332, 1334, 1336,1338, 1340, 1342, 1344 and 1346 of n-type polysilicon. The tiers 1330,1332, 1334, 1336, 1338, 1340, 1342, 1344 and 1346 of polysilicon areseparated from each other by tiers of dielectric such as silicon dioxide(not shown), and the array 1302 and the decoder blocks 1312, 1314, 1316and 1318 are etched into staircase configurations. The tiers 1330, 1332,1334, 1336, 1338, 1340, 1342, 1344 and 1346 of polysilicon in each ofthe first array 1304 and the second array 1306 function as access linesfor memory cells or select gates. U-shaped pillars 1347 extend betweenthe first array 1304 and the second array 1306. Each U-shaped pillar1347 functions as a body (a source, a channel and/or a drain) of amemory cell transistor for each access line that at least partiallysurrounds that U-shaped pillar 1347. Each U-shaped pillar 1347 comprisesa semiconductor material, such as silicon or polysilicon (e.g., a tubeof silicon or polysilicon with a core, where the core may be filled withair or a dielectric material). The top tier 1346 in the first array 1304and the second array 1306 is etched into select gates, and each selectgate is coupled to ends of multiple ones of the U-shaped pillars 1347.

Some of the tiers 1330, 1332, 1334, 1336, 1338, 1340, 1342, 1344 and1346 of polysilicon in each of the decoder blocks 1312, 1314, 1316 and1318 function as a body (a source, a channel and/or a drain) of adecoder transistor that is to be coupled to an access line of a memorycell or a select gate, and some may not be coupled to an access line ora select gate. Polysilicon gates 1350 for the decoder transistors extendthrough holes in the tiers 1330, 1332, 1334, 1336, 1338, 1340, 1342,1344 and 1346 of polysilicon in each of the decoder blocks 1312, 1314,1316 and 1318. 24 lines 1356 (WL0 to WL15 and SG0-7) are shown couplingthe separate portions of individual tiers 1330, 1332, 1334, 1336, 1338,1340, 1342, 1344 and 1346 of polysilicon in each of the first array 1304and the second array 1306 to one of the tiers 1330, 1332, 1334, 1336,1338, 1340, 1342, 1344 and 1346 of polysilicon in a respective one ofthe decoder blocks 1312, 1314, 1316 and 1318. Eight of the lines 1356are shown to couple each of eight select gates formed in the top tier1346 to a respective one of the tiers 1330, 1332, 1334, 1336, 1338,1340, 1342, 1344 and 1346 of polysilicon in a respective one of thedecoder blocks 1312, 1314, 1316 and 1318. The respective coupling of thelines 1356 is provided in Table I, in which WL# indicates an access lineand SG# indicates a select gate. A line 1356 may couple the same tiersto each other, such as shown with respect to WL2 (which is coupled fromtier 1340 in the second array 1306 to the same tier 1340 in the decoderblock 1314). Alternatively, a line 1356 may couple different tiers toeach other, such as shown with respect to WL 11 (which is coupled fromtier 1336 in the first array 1304 to tier 1342 in the decoder block1312. “X” indicates that the bottom three tiers 1330, 1332, 1334 ofpolysilicon in each of the decoder blocks 1312, 1314, 1316 and 1318 arenot coupled to access lines and are unused. As a result, all nine tiers1330, 1332, 1334, 1336, 1338, 1340, 1342, 1344 and 1346 of polysiliconare used as access lines while six tiers 1336, 1338, 1340, 1342, 1344and 1346 of polysilicon are used as decoder transistors. A ratio of ninetiers of polysilicon used as access lines to six tiers of polysiliconused as decoder transistors is shown in FIG. 13 . Other ratios such aseight to five or ten to seven or one to one may also be used. Forexample, one of the decoder blocks 1312, 1314, 1316 and 1318 could beused for other memory cells (not shown) with all tiers of polysilicon inthe remaining decoder blocks being used as decoder transistors. Thedecoder blocks 1312, 1314, 1316 and 1318 may be aligned with the array1302 to accommodate the routing of data lines.

TABLE 1 1312 1316 1304 1306 1314 1318 1346 WL13 SG3 SGO-3 SG4-7 WL5 SG71344 WL12 SG2 WL15 WL0 WL4 SG6 1342 WL11 SG1 WL14 WL1 WL3 SG5 1340 WL10SG0 WL13 WL2 WL2 SG4 1338 WL9 WL15 WL12 WL3 WL1 WL7 1336 WL8 WL14 WL11WL4 WL0 WL6 1334 X X WL10 WL5 X X 1332 X X WL9 WL6 X X 1330 X X WL8 WL7X X

The embodiment of the semiconductor construction 1300 shown in FIG. 13is an example of the semiconductor memory device 100 shown in FIG. 1according to various embodiments of the invention.

FIG. 14 is a top view of a semiconductor construction 1400 according tovarious embodiments of the invention. The semiconductor construction1400 is formed from tiers of polysilicon formed alternately with adielectric. The semiconductor construction 1400 is etched into a firstset of fingers 1402 and a second set of fingers 1408 that areinterdigitally arranged. One or more of the tiers in the semiconductorconstruction 1400 are unbroken, integrally formed tiers of polysiliconthat include a body (a source, a channel and/or a drain) of a peripheraltransistor and an access line of a memory cell or a select gate. One ormore of the unbroken, integrally formed tiers of polysilicon may includea body (a source, a channel and/or a drain) of a peripheral transistorand a body (a source, a channel and/or a drain) of a memory cell or aselect gate according to various embodiments of the invention. Theperipheral transistor can be a decoder transistor. First holes areetched through the tiers of polysilicon of the first set of fingers 1402and the second set of fingers 1408, and first pillars 1410 of asemiconductor material are formed in the first holes to be channels formemory cells. The first pillars 1410 comprise silicon or polysilicon.Lines 1416 are formed in contact with ends of the first pillars 1410 tobe data lines for the first pillars 1410. Second holes are etchedthrough the tiers of polysilicon of the first set of fingers 1402 andthe second set of fingers 1408, and second pillars 1420 of asemiconductor material are formed in the second holes to be select linesfor peripheral transistors such as decoder transistors in the tiers ofpolysilicon. The second pillars 1420 comprise silicon or polysilicon andcan be connected to polysilicon gates of peripheral transistors. Lines1428 are formed in contact with ends of the second pillars 1420. Globalaccess or select lines 1434 are formed in contact with the tiers ofpolysilicon in the first set of fingers 1402 and the second set offingers 1408. The first holes and the second holes are approximately thesame size according to various embodiments of the invention. The lines1416, 1428 and 1434 may be, for example, tungsten, aluminum or copper.The lines 1416, 1428 and 1434 may be replaced by semiconductor linessuch as polysilicon lines.

FIG. 15 is a cross-sectional view of the semiconductor construction 1400according to various embodiments of the invention. The semiconductorconstruction 1400 includes unbroken, integrally formed tiers ofpolysilicon 1510, 1512, 1514, 1516 and 1518 over a silicon substrate1530. The first pillars 1410 extend from the lines 1416 through thetiers 1510, 1512, 1514, 1516 and 1518 to the substrate 1530. The tiers1510 and 1518 include select transistors 1540 (indicated by hiddenlines) to select one or more of the first pillars 1410 passing throughthem. The tiers 1512, 1514 and 1516 are access lines for charge storagedevices 1550 (indicated by hidden lines) for which the first pillars1410 are channels. The first pillars 1410 may be U-shaped pillars thatpass through the substrate 1530 or may end in the substrate 1530. Thesecond pillars 1420 extend from the lines 1428 through the tiers 1510,1512, 1514, 1516 and 1518 and end before the substrate 1530. The secondpillars 1420 are in contact with peripheral transistors 1560 in thetiers 1510, 1512 and 1514. The tiers 1516 and 1518 may also includeperipheral transistors. The lines 1434 extend from the tiers of 1510,1512, 1514, 1516 and 1518. The semiconductor construction 1400 includesmore tiers of polysilicon than are shown in FIG. 15 .

FIG. 16 is a cross-sectional view of the semiconductor construction 1400according to various embodiments of the invention. The first pillars1410 shown in FIG. 16 extend from one of the lines 1416 through thetiers 1510, 1512, 1514, 1516 and 1518 to the substrate 1530. The tiers1512, 1514, 1516 and 1518 are divided into separate portions such thattwo of the first pillars 1410 pass through each of the portions of thetiers 1510, 1512, 1514 and 1516 and each pillar 1410 passes through oneof the portions of the tier 1518. Each of the portions of the tiers 1510and 1518 includes a select gate to select the first pillar or pillars1410 passing through it. The portions of the tiers 1512, 1514 and 1516are access lines for charge storage devices for which the first pillars1410 are channels.

The embodiments of the semiconductor construction 1400 shown in FIGS. 14to 16 are examples of the semiconductor memory device 100 shown in FIG.1 according to various embodiments of the invention.

FIG. 17 is a perspective view of a semiconductor memory device 1700according to various embodiments of the invention. The memory device1700 includes horizontal nandstrings of charge storage devices. Bodies(each may include a source, a channel and/or a drain) of the chargestorage devices of a nandstring are shared in a horizontal bar 1710 of asemiconductor material such as polysilicon. The memory device 1700includes multiple horizontal bars 1710 separated from each other byhorizontal dielectrics 1716. Each horizontal bar 1710 may have arectangular or a circular cross-section. Each horizontal bar 1710includes the bodies of twelve charge storage devices, although thehorizontal bars 1710 may support a different number of charge storagedevices. Eight horizontal bars 1710 are arranged in a vertical plane,and each horizontal bar 1710 in a vertical plane is connected at a firstend to a first vertical pillar 1720 of semiconductor material such aspolysilicon that is a common source line (CSL) which is a voltagesource. Each horizontal bar 1710 in the plane is connected at a secondend to a second vertical pillar 1730 of semiconductor material such aspolysilicon that is a data line for the charge storage devices in theplane. The bodies of the charge storage devices in each horizontal bar1710 are aligned with the bodies above and below them in the verticalplane, and third vertical pillars 1740 of semiconductor material such aspolysilicon function as access lines for charge storage devices in thevertical plane. Each third vertical pillar 1740 is an access line forone charge storage device associated with each horizontal bar 1710 andextends through all of the horizontal bars 1710 in the vertical plane.Six vertical planes of horizontal bars 1710 are shown in FIG. 17 as asingle memory device, although the memory device 1700 may include adifferent number of horizontal bars 1710 and associated charge storagedevices. The second vertical pillars 1730 change direction and havehorizontal portions 1760 that pass underneath the semiconductorconstruction 1700. The horizontal portions 1760 of the second verticalpillars 1730 extend the data lines in a horizontal directionsubstantially parallel with the horizontal bars 1710.

FIG. 18 is a schematic view of a semiconductor construction 1800according to various embodiments of the invention. The semiconductorconstruction 1800 comprises an array 1802 of memory cells and sevendecoder blocks 1812, 1814, 1816, 1818, 1820, 1822 and 1824 of decodertransistors. The decoder blocks 1812, 1814, 1816, 1818, 1820, 1822 and1824 each comprise multiple decoder transistors with polysilicon gates1828, and have a staircase configuration. The array 1802 comprisesbodies of memory cells, each comprising a source, a channel and/or adrain, formed in respective horizontal bars 1830 of semiconductormaterial, such as n-type polysilicon. Access lines 1840 are formed incontact with the cells in the horizontal bars 1830. The access lines1840 are vertical pillars of a semiconductor material, such as n-typepolysilicon. Each access line 1840 is coupled to a respective decodertransistor in a respective one of the decoder blocks 1812, 1814, 1816and 1818 through a respective one of conductive lines 1850. Eachhorizontal bar 1830 is coupled to a respective decoder transistor in arespective one of the decoder blocks 1820, 1822 and 1824 through arespective one of data lines 1860. The decoder blocks 1816 and 1818 canbe aligned with the array 1802 of memory cells. The decoder blocks 1812and 1814 may also be aligned with the array 1802 of memory cellsaccording to various embodiments of the invention.

FIG. 19 is a cross-sectional view of the semiconductor construction 1800according to various embodiments of the invention. The horizontal bars1830 with the bodies of memory cells are located over a siliconsubstrate 1930. Cross-sectional views of the access lines 1840 are shownthat are substantially orthogonal to the horizontal bars 1830. Theaccess lines 1840 are substantially square, but may have a differentgeometry. Each access line 1840 has a first contact 1950 that extends tointersect with a plurality of the horizontal bars 1830. A charge storagedevice 1956 (indicated by hidden lines) is located at each intersectionof a horizontal bar 1830 with a first contact 1950, and the firstcontacts 1950 may be separated from the horizontal bars 1830 by adielectric such as silicon dioxide. Each horizontal bar 1830 is coupledto a data line 1860 through a second contact 1970. The first contacts1950 and the second contacts 1970 comprise metal or polysilicon. Thesemiconductor construction 1800 includes more horizontal bars 1830 andmore access lines 1840 than are shown in FIG. 19 according to variousembodiments of the invention.

FIG. 20 is a cross-sectional view of the semiconductor construction 1800according to various embodiments of the invention. Cross-sectional viewsof the horizontal bars 1830 and the data lines 1860 are illustrated inFIG. 20 , and each data line 1860 is coupled to four of the horizontalbars 1830 by one of the second contacts 1970. The access lines 1840 andthe data lines 1860 are substantially square, but may have differentgeometries. One of the access lines 1840 is shown between the siliconsubstrate 1930 and the horizontal bars 1830, and the first contacts 1950extend from the access line 1840 toward the horizontal bars 1830. Acharge storage device is located at each intersection between ahorizontal bar 1830 and a first contact 1950, such as the charge storagedevice 2010 (indicated by hidden lines). The first contacts 1950 may beseparated from the horizontal bars 1830 by a dielectric such as silicondioxide. The semiconductor construction 1800 includes more horizontalbars 1830 and more access lines 1840 than are shown in FIG. 20 accordingto various embodiments of the invention.

The embodiments of the semiconductor construction 1800 shown in FIGS. 18to 20 are examples of the semiconductor memory device 1700 shown in FIG.17 according to various embodiments of the invention.

FIG. 21 is a cross-sectional view of a semiconductor memory device 2100according to various embodiments of the invention. The semiconductorconstruction 2100 includes charge trap layers arranged around twopolysilicon pillars 2110 formed on a p-type silicon substrate 2114. Eachpillar 2110 extends between the substrate 2114 and a conductive plug2118. The conductive plugs 2118 comprise metal or polysilicon. The metalmay be, for example, titanium nitride (TiN), tantalum (Ta), tantalumnitride (TaN) or Tungsten (W). The conductive plugs 2118 are inelectrical contact with a data line 2120. The data line 2120 is at adrain end of the pillars 2110 and the substrate 2114 is at a source endof the pillars 2110. Current flows from the data line 2120 through thepillars 2110 to the substrate 2114 during powered operation of thesemiconductor construction 2100.

Data is stored in a charge trap layer 2130 that surrounds each pillar2110. Each charge trap layer 2130 has a serpentine pattern includingfirst portions 2134 of the charge trap layer 2130 that are in contactwith the pillar 2110 and second portions 2138 of the charge trap layer2130 that are separated from the pillar by a dielectric 2142. Thedielectric 2142 may comprise, for example, silicon dioxide (SiO₂),oxynitride or nitrided oxide. Each charge trap layer 2130 comprises alayer of silicon dioxide (SiO₂) that is a tunnel oxide layer closest tothe pillar 2110. A trap layer of silicon nitride (Si₃N₄) is formed onthe tunnel oxide layer, and a blocking layer is formed on the traplayer. The blocking layer may comprise silicon nitride (Si₃N₄) betweentwo layers of silicon dioxide (SiO₂) that together comprise aninter-poly dielectric (IPD) layer of oxide-nitride-oxide (SiO₂Si₃N₄SiO₂or “ONO”). Control gates 2146 surround each pillar 2110 in contact withrespective ones of the first portions 2134 of the charge trap layer 2130that are in contact with the pillar 2110. The control gates 2146comprise metal or polysilicon. A potential of one or more of the controlgates 2146 may be raised to store charge or read data in the respectivefirst portions 2134 of the charge trap layer 2130. With reference to thedecoder transistors 1100 shown in FIG. 11 , the gates 1160 of thedecoder transistors 1100 can be formed with the pillars 2110. Inaddition, the three tiers 1110, 1120 and 1130 of polysilicon includingthe sources 1180 and the drains 1170 of the decoder transistors 1100 canbe formed with the control gates 2146 of the memory device 2100according to various embodiments of the invention.

FIG. 22 is a cross-sectional view of a semiconductor memory device 2200according to various embodiments of the invention. Charge storagedevices of a nandstring are formed on a stack 2210 of four alternatinglayers of access lines 2214 and isolating films 2218. A gate dielectricand a channel 2226 of polysilicon are formed over the stack 2210 ofaccess lines 2214 and isolating films 2218. The channel 2226 compriseseight charge storage devices controlled by the four access lines 2214 inthe stack 2210. Each access line 2214 controls two charge storagedevices in the channel 2226, one on each side of the stack 2210. Eachchannel 2226 is controlled by a source select line (SSL) transistor 2240at a first end and a ground select line (GSL) transistor 2250 at asecond end. Each GSL transistor 2250 is coupled to a line 2252 toreceive a supply voltage and each SSL transistor 2240 is coupled to adata line 2260. Each access line 2214 is coupled to a metal terminal2270. Each channel 2226 is formed over three stacks 2210 of access lines2214, and each stack 2210 of access lines 2214 extends under threeseparate and substantially parallel channels 2226 such that thesemiconductor construction 2200 comprises 72 charge storage devices. Thechannels 2226 may comprise a semiconductor material other thanpolysilicon. The semiconductor memory device 2200 may include adifferent number of channels 2226 and the stacks 2210 of access lines2214 may be longer to extend under more channels 2226. With reference tothe decoder transistors 1100 shown in FIG. 11 , the gates 1160 of thedecoder transistors 1100 can be formed with the access lines 2214. Inaddition, the three tiers 1110, 1120 and 1130 of polysilicon includingthe sources 1180 and the drains 1170 of the decoder transistors 1100 canbe formed with the channels 2226 according to various embodiments of theinvention.

FIG. 23 is a flow diagram of methods 2300 according to variousembodiments of the invention. In block 2310, the methods 2300 start. Inblock 2320, a plurality of tiers of semiconductor material, such asn-type polysilicon, are formed. In block 2330, an access line of amemory cell is formed in a tier of the semiconductor material (e.g.,n-type polysilicon). In block 2340, a source, a channel and/or a drainof a peripheral transistor, such as a decoder transistor, are formed inthe same tier of n-type polysilicon. This process can be repeated foreach tier. In block 2350, a source or drain of a peripheral transistoris coupled to one of the access lines. In block 2360, the methods 2300end. Various embodiments may have more or fewer activities than thoseshown in FIG. 23 . In some embodiments, the activities may be repeated,substituted one for another, and/or performed in serial or parallelfashion.

FIG. 24 is a diagram illustrating a system 2400 according to variousembodiments of the invention. The system 2400 may include a processor2410, a memory device 2420, a memory controller 2430, a graphiccontroller 2440, an input and output (I/O) controller 2450, a display2452, a keyboard 2454, a pointing device 2456, and a peripheral device2458. A bus 2460 couples all of these devices together. A clockgenerator 2470 is coupled to the bus 2460 to provide a clock signal toat least one of the devices of the system 2400 through the bus 2460. Theclock generator 2470 may include an oscillator in a circuit board suchas a motherboard. Two or more devices shown in system 2400 may be formedin a single integrated circuit chip. The memory device 2420 may compriseone of the memory devices 100, 1700, 2100 or 2200 described herein andshown in the figures according to various embodiments of the invention.The memory device 2420 may comprise a semiconductor construction 2482 or2484 such as, for example, one or more of the semiconductorconstructions 200, 1300, 1400 and 1800 described herein and shown in thefigures according to various embodiments of the invention. The bus 2460may be interconnect traces on a circuit board or may be one or morecables. The bus 2460 may couple the devices of the system 2400 bywireless means such as by electromagnetic radiations, for example, radiowaves. The peripheral device 2458 coupled to the I/O controller 2450 maybe a printer, an optical device such as a CD-ROM and a DVD reader andwriter, a magnetic device reader and writer such as a floppy diskdriver, or an audio device such as a microphone.

The system 2400 represented by FIG. 24 may include computers (e.g.,desktops, laptops, hand-helds, servers. Web appliances, routers, etc.),wireless communication devices (e.g., cellular phones, cordless phones,pagers, personal digital assistants, etc.), computer-related peripherals(e.g., printers, scanners, monitors, etc.), entertainment devices (e.g.,televisions, radios, stereos, tape and compact disc players, videocassette recorders, camcorders, digital cameras. MP3 (Motion PictureExperts Group, Audio Layer 3) players, video games, watches, etc.), andthe like.

Example structures and methods of fabricating semiconductor devices havebeen described. Although specific embodiments have been described, itwill be evident that various modifications and changes may be made tothese embodiments. Accordingly, the specification and drawings are to beregarded in an illustrative rather than a restrictive sense.

The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that allows the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit theclaims. In addition, in the foregoing Detailed Description, it may beseen that various features are grouped together in a single embodimentfor the purpose of streamlining the disclosure. This method ofdisclosure is not to be interpreted as limiting the claims. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

What is claimed is:
 1. A method of forming a memory structure,comprising: forming multiple vertically arranged conductive tiersvertically separated from one another by respective dielectric tiers,each conductive tier extending in a memory array area and in aperipheral area; in the peripheral area, forming a body of a respectiveperipheral transistor in a plurality of the multiple conductive tiers;forming first pillars comprising semiconductor material extendingvertically through the multiple vertically arranged conductive tiers inthe memory array area; and forming second pillars comprisingsemiconductor material extending vertically through the multiplevertically arranged tiers in the peripheral area, the second pillarsforming a gate of at least one peripheral transistor.
 2. The method ofclaim 1, further comprising initially forming the multiple verticallyarranged conductive tiers of material comprising polysilicon.
 3. Themethod of claim 2, further comprising: masking a first portion of thematerial comprising polysilicon of the conductive tiers extending in theperipheral area; and replacing a second portion of the materialcomprising polysilicon of the conductive tiers extending in the memoryarray area with a metal-comprising material to form access lines of amemory array.
 4. The method of claim 3, forming memory cells in thememory array area, comprising forming multiple vertically arrangedmemory cells adjacent respective first pillars to form a memory arraycomprising multiple vertical strings of memory cells.
 5. The method ofclaim 4, wherein the memory cells in the memory array area are chargestorage memory cells.
 6. The method of claim 5, wherein the chargestorage memory cells are floating gate memory cells.
 7. The method ofclaim 5, wherein the charge storage memory cells are charge trap memorycells.
 8. The method of claim 4, wherein the metal comprising materialforming access lines of the memory array forms control gates of memorycells in multiple vertical strings of memory cells.
 9. The method ofclaim 8, wherein the access lines of the memory array are coupled torespective peripheral transistors in the peripheral area.
 10. The methodof claim 9, wherein the respective peripheral transistors to which theaccess lines are coupled are decoder transistors.
 11. The method ofclaim 3, wherein first pillars in the memory array area are formed in aU-shape.
 12. The method of claim 3, further comprising, before replacingthe material comprising polysilicon of the conductive tiers extending inthe memory array area with a metal-comprising material, forming a slotthrough the conductive tiers comprising polysilicon to separate thememory array area from the peripheral area.
 13. The method of claim 12,wherein the metal-comprising material forming the access lines includestitanium nitride, tantalum, tantalum nitride or tungsten.
 14. A method,comprising: forming multiple vertically-spaced tiers of a semiconductormaterial; forming respective memory cells in at least two of thevertically-spaced tiers of the semiconductor material in a memory arrayarea to form strings of memory cells; forming a respective portion ofrespective peripheral transistors in at least two of the tiers of thesemiconductor material in a peripheral area, wherein forming therespective portion of peripheral transistors includes forming at leastone of a respective source, channel, or drain of the peripheraltransistor in a respective tier of semiconductor material; forming aslot between the memory array area and the peripheral area separatingthe vertically spaced tiers of semiconductor material between the twoareas; replacing the semiconductor material of the vertically spacedtiers in the memory array area with a material comprising metal to formaccess lines, the access lines each extending to memory cells inmultiple strings; and coupling the access lines with respectiveperipheral transistors.
 15. The method of claim 14, further comprisingforming first pillars of semiconductor material in the memory arrayarea, wherein the respective strings of memory cells are verticalstrings which include a respective pillar of the first pillars ofsemiconductor material.
 16. The method of claim 15, wherein the firstpillars include U-shaped pillars.
 17. The method of claim 14, furthercomprising forming second pillars of semiconductor material in theperipheral area, wherein the second pillars form a gate of a peripheraltransistor.
 18. The method of claim 17, wherein the second pillars forma gate of a decoder transistor.
 19. The method of claim 14, furthercomprising forming the access lines in the memory array area into afirst staircase configuration.
 20. The method of claim 19, furthercomprising forming the semiconductor material of the vertically spacedtiers in the peripheral area into a second staircase configuration.